As with EC2 and S3, Amazon charges fees for SimpleDB storage, transfer, and throughput over the Internet. On December 1, 2008, Amazon introduced new pricing with Free Tier[3] for 1 GB of data & 25 machine hours. Transfer to other Amazon Web Services is free of charge.[4]

SimpleDB provides eventual consistency, which is a weaker form of consistency, compared to other database management systems. This is often considered a limitation, because it is harder to reason about, which makes it harder to write correct programs that make use of SimpleDB. This limitation is the result of a fundamental design trade-off. By foregoing consistency, the system is able to achieve two other highly desirable properties:

availability - components of the system may fail, but the service will continue to operate correctly.

partition tolerance - components in the system are connected to one another by a computer network. If components are not able to contact one another using the network (a condition known as a network partition), operation of the system will continue.

Component failures are assumed to be inevitable; thus, both of these properties were deemed necessary in order to provide a reliable web service. The CAP theorem states that it is not possible for a system to exhibit these properties along with consistency; thus, the designers needed to settle for a weaker form of consistency.

250 active domains per account. More can be requested by filling out a form.[6]

size of each domain

10 GB

attributes per domain

1,000,000,000

attributes per item

256 attributes

size per attribute

1024 bytes

Query limitations

Attribute

Maximum

items returned in a query response

2500 items

seconds a query may run

5 seconds

attribute names per query predicate

1 attribute name

comparisons per predicate

22 operators

predicates per query expression

20 predicates

Features

Conditional Put and Delete

Conditional put and conditional delete are new operations that were added in February 2010. They address a problem that arises when accessing SimpleDB concurrently. Consider a simple program that uses SimpleDB to store a counter, i.e. a number that can be incremented. The program must do three things:

Retrieve the current value of the counter from SimpleDB.

Add one to the value.

Store the new value in the same place as the old value in SimpleDB.

If this program runs while no other programs access SimpleDB, it will work correctly; however, it is often desirable for software applications (particularly web applications) to access the same data concurrently. When the same data is accessed concurrently, a race condition arises, which would result in undetectable data loss.

Continuing the previous example, consider two processes, A and B, running the same program. Suppose SimpleDB services requests for data, as described in step 1, from both A and B. A and B see the same value. Let's say that the current value of the counter is 0. Because of steps 2 and 3, A will try to store 1. B will try to do the same; thus, the final counter value will be 1, even though the expected final counter value is 2, because the system attempted two increment operations, one by A, and another by B.

This problem can be solved by the use of conditional put. Suppose we change step 3 as follows: instead of unconditionally storing the new value, the program asks SimpleDB to store the new value only if the value that it currently holds is the same as the value that was retrieved in step 1. Then, we can be sure that the counter's value actually increases. This introduces some additional complexity; if SimpleDB was not able to store the new value because the current value was not as expected, the program must repeat steps 1-3 until the conditional put operation actually changes the stored value.

Consistent Read

Consistent read was a new feature that was released at the same time as conditional put and conditional delete. As the name suggests, consistent read addresses problems that arise due to SimpleDB's eventual consistency model (See the Limitations section). Consider the following sequence of operations:

Program A stores some data in SimpleDB.

Immediately after, A requests the data it just stored.

SimpleDB's eventual consistency guarantee does not allow us to say that the data retrieved in step 2 reflects the updates that were made in step 1. Eventual consistency only guarantees that step 2 reflects the complete set of updates in step 1, or none of those updates. Consistent read can be used to ensure that the data retrieved in step 2 reflect changes in step 1.

The reason that inconsistent results can arise when the consistent read operation is not used is that SimpleDB stores data in multiple locations (for availability), and the new data in step 1 might not be written at all locations when SimpleDB receives the data request in step 2. In that case, it is possible that the data request in step 2 is serviced at one of the locations where the new data has not been written.

Amazon discourages the use of consistent read, unless it is required for correctness. The reason for this recommendation is that the rate at which consistent read operations are serviced is lower than for regular reads.

This is official Amazon Web Services (AWS) documentation for Amazon SimpleDB. Amazon SimpleDB is a web service for running queries on structured data in real time. This service works in close conjunction with Amazon Simple Storage Service (Amazon S3) and Amazon Elastic Compute Cloud (Amazon EC2), collectively providing the ability to store, process and query data sets in the cloud. These services are designed to make web-scale computing easier and more cost-effective for developers. This guide provides a conceptual overview of Amazon SimpleDB and includes detailed development instructions for using the various features. This documentation is offered for free here as a Kindle book, or you can read it online or in PDF format at https://aws.amazon.com/documentation/simpledb/.

The Complete Guide to Building Cloud Computing Solutions with Amazon SimpleDB

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Using SimpleDB, any organization can leverage Amazon Web Services (AWS), Amazonâs powerful cloud-based computing platformâand dramatically reduce the cost and resources associated with application infrastructure. Now, for the first time, thereâs a complete developerâs guide to building production solutions with Amazon SimpleDB.

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Pioneering SimpleDB developer Mocky Habeeb brings together all the hard-to-find information you need to succeed. Mocky tours the SimpleDB platform and APIs, explains their essential characteristics and tradeoffs, and helps you determine whether your applications are appropriate for SimpleDB. Next, he walks you through all aspects of writing, deploying, querying, optimizing, and securing Amazon SimpleDB applicationsâfrom the basics through advanced techniques.

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Throughout, Mocky draws on his unsurpassed experience supporting developers on SimpleDBâs official Web forums. He offers practical tips and answers that canât be found anywhere else, and presents extensive working sample codeâfrom snippets to complete applications.

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With A Developerâs Guide to Amazon SimpleDB you will be able to

Evaluate whether a project is suited for Amazon SimpleDB

Write SimpleDB applications that take full advantage of SimpleDBâs availability, scalability, and flexibility

If you plan to use Amazon Web Services to run applications in the cloud, the end-to-end approach in this book will save you needless trial and error. You'll find practical guidelines for designing and building applications with Amazon Elastic Compute Cloud (EC2) and a host of supporting AWS tools, with a focus on critical issues such as load balancing, monitoring, and automation.

How do you move an existing application to AWS, or design your application so that it scales effectively? How much storage will you require? Programming Amazon EC2 not only helps you get started, it will also keep you going once you're successfully positioned in the cloud. This book is a must-read for application architects, developers, and administrators.

This focused book is an extracted LITE version of Packtâs full: Amazon SimpleDB Developer Guide. It concentrates on getting a grounding in the value of SimpleDB, and shows how to set up an AWS account, enable a SimpleDB service for the account, and install and set up libraries for Java, PHP, and Python. If you are a developer wanting to get to grips with a primer into SimpleDB, then this book is for you. You do not need to know anything about SimpleDB to read and learn from this book, and no basic knowledge is strictly necessary.

This book is a practical real-world tutorial covering everything you need to know about Amazon SimpleDB. You will come across examples in three languages: Java, PHP, and Python. This book is aimed at transforming you from a beginner to an advanced developer. If you are a developer wanting to build scalable web-based database applications using SimpleDB, then this book is for you. You do not need to know anything about SimpleDB to read and learn from this book, and no basic knowledge is strictly necessary. This guide will help you to start from scratch and build advanced applications.

A comprehensive look at the emerging Amazon Web Services Platform and a peep into the emerging paradigm of cloud computing from the perspective of the leading Cloud vendors offerings. It will enable you to plan migration efforts from enterprise softwares to ones operating from the cloud. The book is technical in nature and walks the reader through development of tools and programs which work with AWS. The book is accompanied by the complete source code to the excercises covered in the book, which can be downloaded from the authors website. 'A no fluff just stuff' approach to utilizing AWS.

- Differences between traditional development and developing for the Cloud. Especially Amazon Web Services- The whole gamut of AWS api's and use it for Automation, Monitoring, Development and Management- The platform & tools offered by AWS- The techniques needed to utilize AWS effectively- How to program for AWS- How to adapt Agile practices to AWS. Specifically continous integration.

Who is this book for?

This book is for CXO and leaders to quickly glance through and understand the Amazon Web Services offerings. And for developers, QA, analysts, administrators and managers to get started with AWS.

About the Author

Aditya has been involved with Software Engineering before the time Internet came to India in 1992-1993. During his more than a decade of industry stint he has played the roles of developer, analyst, product manager through CTO. He is the founder of one of the top 25 startups in India. Before he took his sabbatical to write this book he was a Sr. Architect at Thoughtworks. And is a well known Agile coach. Leads an independant consulting company Aditya Yadav & Associates which offers Technology and Technology strategy consulting services to Fortune companies. He is a contrarian when it comes to SOA & EAI on which he believes there is no need for Governance or COE's and has proven his approach over the years successfully. Aditya is a Cloud Computing evangelist and has been following this space since Amazon launched AWS. He is technology, platform and domain agnostic and specialises in Internet Scale Architectures.

When he is not doing something related to software development. He is busy composing music, learning guitar and swimming. Aditya has been a long distance 24 hour swimmer since his college days. He has a B.Tech and M.Tech degree fromIndian Institute Of Technology, Bombay, India.

Developed Strategies and Processes that Enabled Brands to Grow During an Economic Downturn.

Taught Advanced Internet Marketing Strategies at the graduate level.

Manage research, learning and skills at defaultLogic. Create an account using LinkedIn or facebook to manage and organize your IT knowledge. defaultLogic works like a shopping cart for information -- helping you to save, discuss and share.

Manage research, learning and skills at defaultLogic. Create an account using LinkedIn or facebook to manage and organize your IT knowledge. defaultLogic works like a shopping cart for information -- helping you to save, discuss and share.